1. Field of the Invention
The present invention relates to a head mounted display (HMD) and more particularly, to a head mounted display having light emitting devices.
2. Background of the Invention
A head mounted display (HMD) refers various types of image display devices worn on a user's head in the form of eyewear glasses, and configured to allow a user to see images (content) therethrough. As digital devices become lighter and smaller, various wearable computers are being developed and the HMD is being widely used. The HMD may provide a user not only with a display function, but also with various functions by combining an augmented reality (AR) technique, an N screen technique, and the like.
As usage of the HMD is increased nowadays, methods of executing various functions according to a posture of the HMD are actively researched. The posture of the HMD includes a mounted state of the HMD to a user's head, a tilted degree of the HMD, a direction that the HMD faces, a position of the HMD, rotation of the HMD, movement of the HMD, and the like.
In order to determine (estimate, trace, detect, extract, recognize, or identify) the posture of the HMD, light emitting devices and a camera may be provided.
In the conventional art, an open close time (frame) of a shutter of a camera is synchronized with an on/off time (frame) of light emitting devices of the HMD. More specifically, in the conventional art, a plurality of light emitting devices are disposed at any position on the HMD, and each of the plurality of light emitting devices is set to have a different on/off pattern. An ‘on’ state of the light emitting device means that the light emitting device emits light, whereas an ‘off’ state of the light emitting device means that the light emitting device does not emit light.
For example, assuming that an ‘on’ state of the light emitting device is ‘1’, an ‘off’ state of the light emitting device is ‘0’, and each on/off pattern has 10 frames, any first light emitting device among a plurality of light emitting devices is set to emit light so as to have a first pattern (e.g., ‘1100101011’), and any second light emitting device among the plurality of light emitting devices is set to emit light so as to have a second pattern (e.g., ‘1110010011’).
Further, in the conventional art, the camera and the HMD are synchronized with each other such that an open close time (frame) of the shutter of the camera is synchronized with an on/off time (frame) of the light emitting devices of the HMD. Then, the on/off pattern of each of the plurality of light emitting devices is determined by the synchronized camera, thereby recognizing each light emitting device. And a posture of the HMD is determined by using the recognized light emitting device.
In case of using such a synchronization method, an additional configuration (e.g., synchronization cable) is required to synchronize an open close time (frame) of the shutter of the camera with an on/off time (frame) of the light emitting devices of the HMD. Thus, this configuration may increase the fabrication costs.
Furthermore, in case of using such a synchronization method, as the number of the light emitting devices of the HMD is increased, the number of frames to form the pattern is also increased. This may cause a long time to be taken to determine a posture of the HMD. Thus, various methods of determining a posture of the HMD are required nowadays.